In any legal action based upon a cause of action arising on or after July 1, 1987, every pleading, motion, and other paper of a party represented by an attorney shall be signed by at least one attorney of record in his or her individual name, whose address and telephone number shall be stated. A party who is not represented by an attorney shall sign his or her pleading, motion, or other paper and state his or her address and telephone number. Except when otherwise specifically provided by rule or statute, pleadings need not be verified or accompanied by affidavit. The signature of an attorney or party constitutes a certificate by him or her that he or she has read the pleading, motion, or other paper; that to the best of his or her knowledge, information, and belief formed after reasonable inquiry it is well grounded in fact and is warranted by existing law or a good faith argument for the extension, modification, or reversal of existing law, and that it is not interposed for any improper purpose, such as to harass or to cause unnecessary delay or needless increase in the cost of litigation. If a pleading, motion, or other paper is not signed, it shall be stricken unless it is signed promptly after the omission is called to the attention of the pleader or movant. If a pleading, motion, or other paper is signed in violation of this rule, the court, upon motion or upon its own initiative, may impose upon the person who signed it, a represented party, or both, an appropriate sanction, which may include an order to pay to the other party or parties the amount of the reasonable expenses incurred because of the filing of the pleading, motion, or other paper, including a reasonable attorney’s fee.